Pharmaceutical Drug Analysis - جامعة الناصر

(x) an attempt at minimizing systematic errors. The second aspect is mainly devoted to statistical validation and comprises of statistical treatment of finite samples, distribution of random errors, significant errors, comparison of results, method of least squares and criteria for rejection of an observation. The various modern techniques involved in Pharmaceutical Drug Analysis mostly covered in the official compendia have been adequately dealt with in Part II through Part VI and systematically spread over from Chapter 4 through Chapter 32 in the present textual compilation. Each chapter has its unique style of presentation that essentially comprises of the following vital features, namely : brief introduction, theory with necessary details and relevant reactions, instrumentation, assay methods—with typical appropriate examples invariably selected from the Official Compendia including brief theoretical treatment of individual pharmaceutical substance and dosage form, materials required, procedures, calculations wherever applicable, cognate assays and lastly citation of relevant literature under ‘Recommended Readings’. Part—II contains twelve chapters under the broad category of ‘Chemical Methods’. Section— A deals on treatment by ‘titrimetric methods’ based on acidimetry and alkalimetry. The first arm of this section deliberates on aqueous titrations (Chapter 4), while the second on non-aqueous titrations (Chapter 5). Section—B relates to ‘redox methods’ with specific reference to permanganate, dichromate and ceric sulphate titration methods (Chapter 6); and also the iodimetric and iodometric titrations (Chapter 7). Section—C concerns with the ‘precipitation methods’ and focuses on argentometric methods (Chapter 8). Section—D comprises the ‘complexometric methods’ using organic ligands, such as EDTA. Particular stress has been laid on the effect of pH on complexation, stability of complexes, usage of pM indicators and masking and demasking agents (Chapter 9). Section—E solely embodies the conventional ‘gravimetric methods’. The topic has been treated with respect to Law of Mass Action, reversible reactions, principle of solubility of product and common-ion effect. Typical examples have been included of pharmaceutical substances assayed after conversion to free acid, or free base, or free compound and lastly to derivatives or substitution products (Chapter 10). Section— F is entirely devoted to ‘thermoanalytical methods’ consisting mainly of thermogravimetric analysis (TGA), differential thermal analysis (DTA) and lastly thermometric titrations (TT) (Chapter 11). Section—G particularly embodies the ‘miscellaneous methods’ which do not fall into the regimen of Section—A through Section—F. It deals with diazotization (Chapter 12), estimation of phenols and related compounds (Chapter 13) using bromine or potassium bromate, potassium iodate solutions; Karl Fischer method for determination of water (Chapter 14); and lastly tetrazolium assay of steroids (Chapter 15). Part—III exclusively treats ‘Electrochemical Methods’ invariably and extensively used in the analysis of pharmaceutical substances in the Official Compendia. Two important methods, namely; potentiometric methods (Chapter 16) deal with various types of reference electrodes and indicator electrodes, automatic titrator; besides typical examples of nitrazepam, allopurinol and clonidine hydrochloride. Amperometric methods (Chapter 17) comprise of titrations involving dropping-mercury electrode, rotating—platinum electrode and twin-polarized microelectrodes (i.e., dead-stop-end-point method). Part—IV has been entirely devoted to various ‘Optical Methods’ that find their legitimate recognition in the arsenal of pharmaceutical analytical techniques and have been spread over nine chapters. Refractometry (Chapter 18) deals with refractive index, refractivity, critical micelle concentration (CMC) of various important substances. Polarimetry (Chapter 19) describes optical rotation and specific optical rotation of important pharmaceutical substances. Nephelometry and turbidimetry (Chapter 20) have been treated with sufficient detail with typical examples of chloroetracyclin, sulphate and phosphate ions. Ultraviolet and absorption spectrophotometry (Chapter 21) have been discussed with adequate depth and with regard to various vital theoretical considerations, single-beam and double-beam spectrophotometers; besides typical examples amoxycillin trihydrate, folic acid, glyceryl trinitrate tablets and stilbosterol. Infrared spectrophotometry (IR) (Chapter 22) essentially deals with a brief introduction of group-frequency

( xi ) region and fingerprint region followed by detailed theoretical aspects covering molecular vibrations and factors influencing vibrational frequencies. Having described the single monochromator infrared spectrophotometers, the applications of IR-spectroscopy have been discussed with respect to pharmaceutical substances and pharmaceutical dosage forms. Analytical aspects of IR-spectroscopy have also been treated adequately for the determination of cis-trans isomer ratio in clomiphene citrate, distinction of pri-, sec- and tert-amine salts from one another, studying complex formations and quantitative reaction sequences, identification of functional groups and fingerprinting. Nuclear resonance spectroscopy (NMR) (Chapter 23) treats the subject with regard to the NMR-phenomenon and proton-NMR. Various theoretical aspects viz., orientations of magnetic nucleus under external-magnetic field (Bo), precessional frequency, saturation of the signal, absorption positions in NMR-spectrum, chemical shift, spin-spin interactions, 3H-NMR, 13C-NMR and 2D-NMR. Special emphasis has been given to the interpretation of a NMR-spectrum, chemical shift, relative peak area, multiplicity of the signal and coupling constant. Instrumentation has been dealt adequately. Applications of NMR-spectroscopy in pharmaceutical analysis, identification testing and assay of drugs have been treated so as to justify their vital importance in modern methods of analysis. Emission spectroscopy (Chapter 24) provides a brief introduction, theory and instrumentation with regard to its excitation sources, electrodes, sample handling, monochromators, detectors, spectrographs and its applications. Flame spectroscopy (Chapter 25) widely used in the quantitative estimation of various elements e.g., Na, K, Ca, Ba has also been included. Both simple flame photometer and internal-standard flame photometer have been discussed in sufficient detail. The assay of Na, K and Ca in blood serum and water; assay of Ba, K and Na in calcium lactate have been described followed by cognate assays. Atomic absorption spectroscopy (AAS) (Chapter 26) treats this versatile aspect of analytical technique at length. It deals with the merits of AAS Vs Flame Emission Spectroscopy (FES) specifically treats both the single-beam and the double-beam AAS followed by the dements of AAS. Instrumentation specifically treats both the single-beam and the double-beam AAS. The various aspects of AAS e.g., analytical techniques, detection limit and sensitivity, and interference have been duly covered. A few typical examples of AAS in pharmaceutical analysis e.g., Zn in Insulin-Zinc Suspension, Pd in Carbenicillin Sodium have been described followed by cognate assays. Part—V is solely confined to the ‘Assay Methods based on Separation Techniques’ and is spread over five chapters. Liquid-liquid extraction (Chapter 27) mostly treats the subject theoretically and is supported by appropriate examples. Errors due to the volume change and effectiveness of an extraction have been dealt with adequately. Various factors that influence solvent extraction, such as : temperature and inert solutes, pH ion-pair formation and synergistic extraction have been described. A number of typical assay methods, for instance : Cu (I) as the neo-cuproin complex, Fe (III) as the 8-hydroxy quinolate complex, Pb (I) by the dithizone method, Mo (VI) by the thiocyanate method and Ni (II) as dimethylglyoxime complex and by synergistic extraction have been discussed. Thin-layer chromatography (TLC) (Chapter 28) illustrates the versatility of this technique over paper and column chromatography. Various aspects of experimental techniques of TLC viz., preparation of thin layers on plates, choice of adsorbents and solvent systems, activation of adsorbent, purification of adsorbent layers, spotting of components, development of thin layers, special techniques in TLC, chemical reactions on TLC plates, combination of TLC with other techniques and finally detection and evaluation of chromatograms have been expatiated profusely with examples. Applications of TLC in pharmaceutical analysis have been discussed in sufficient length. Gas-liquid chromatography (GLC) (Chapter 29) exclusively treats the subject with regard to various theoretical aspects, namely: plate theory, rate theory, random walk and nonequilibrium theory. Instrumentation comprises mainly different vital components. The working techniques for quantitative analysis e.g., area normalization and internal standard method have been described. Lastly the applications of GLC in pharmaceutical analysis have been described with suitable examples from the Official Compendia. High Performance Liquid Chromatography (HPLC) (Chapter 30) gives an elaborate discussion of theoretical aspects. Instrumentation encompasses the various important components e.g., solvent reservoir and degassing system; pressure, flow and temperature; pumps and sample injection system;

( xii ) columns; detectors; strip-chart recorder; data-handling device and microprocessor control. Another important aspect to facilitate HPLC known as the ‘derivatization’ has been discussed. The applications of HPLC in the assay of drugs, such as: cephalosporins, frusemide, theophylline, corticosteroids, dichlorphenamide, Human Insulin and lastly cognate assays have been fully elaborated. Size Exclusion Chromatography (Chapter 31) has also been included as a means of analysis for substances that undergo separation more or less as per their molecular size, viz., insulin and human insulin—for proteins of higher molecular weight; corticotrophin—for impurities of higher molecular weights; and plasma-protein solution—for polymers and aggregates. Part—VI has been solely devoted to ‘Miscellaneous Assay Methods’ wherein radioimmunoassay (RIA) (Chapter 32) has been discussed extensively. Various arms of theoretical aspects viz., hapten determinants and purity; importance of antigenic determinants; and analysis of competitive antibody binding of isotopically labeled compounds. The applications of RIA in pharmaceutical analysis, such as : morphine, hydromorphone and hydrocordone in human plasma; clonazepam, flurazepam in human plasma; chlordiazepoxide in plasma; barbiturates, flunisolide in human plasma have been described elaborately. Lastly, the novel applications of RIA-techniques, combined RIA-technique-isotope dilution and stereospecificity have also been included to highlight the importance of RIA in the analytical armamentarium. It is earnestly believed that ‘Pharmaceutical Drug Analysis’ will fulfill the entire requirements of both penultimate and final year students of B. Pharm., for their various courses in analytic chemistry in the universities. It may also help the post-graduate students in their compulsory paper on ‘Modern Analytical Techniques’ to a great extent. ‘Pharmaceutical Drug Analysis’ will prove to be a valuable and indispensable guide to those working in Research & Development Laboratories, Quality Assurance Laboratories as well as Drug Testing Laboratories where either new products are being developed or routine analyses are carried out. Academicians and researchers engaged in the evaluation of pharmaceutical drug substances either in pure or dosage forms will also enormously benefit from ‘Pharmaceutical Drug Analysis’ by virtue of its ultimate goal of maintaining very high standards of quantitative analysis. Finally, I wish to record here my special thanks to the numerous colleagues and friends who have not only extended their invaluable help by providing me with relevant sources of material but also by taking an active participation in the discussion of various chapters. It is hoped that ‘Pharmaceutical Drug Analysis’ will soon prove to be an invaluable guide to both undergraduate and postgraduate students and to my esteemed colleagues in the teaching profession. Those working in Research & Development Laboratories, Quality Assurance Laboratories and Drug Testing laboratories will also find the book helpful in solving many of their intricate problems. ASHUTOSH KAR

Contents Preface to the Second Edition . (vii) Preface to the First Edition . (ix) PART I: GENERAL ASPECTS 1. PHARMACEUTICAL CHEMICALS : PURITY AND MANAGEMENT 1.1. 1.2 1.3. Introduction . 3 Purity . 4 1.2.1. Broad-Based Highest Attainable Standard . 4 1.2.2. Biological Response Vs. Chemical Purity . 5 1.2.3. Official Standards vis-a-vis Manufacturing Standards . 5 Management . 6 1.3.1. Description of the Drug or Finished Product . 6 1.3.2. Sampling Procedures and Errors . 6 1.3.3. Bioavailability . 9 1.3.4. Identification Tests . 10 1.3.5. Physical Constants . 11 1.3.6. Limit Tests vis-a-vis Quantitative Determinations . 17 1.3.7. Various Types of Tests for Quantitative Determinations . 17 1.3.8. Limit Tests for Metallic Impurities . 25 1.3.9. Limit Test’s for Acid Radical Impurities . 30 1.3.10. Limit Tests for Non-Metallic Impurities. 37 2. THEORY AND TECHNIQUE OF QUANTITATIVE ANALYSIS 2.1. 2.2. 2.3. 2.4. 3 41 Introduction . 41 Volumetric Analysis . 42 2.2.1. Theory . 42 2.2.2. Definitions. 42 2.2.3. Volumetric Apparatus . 44 2.2.4. General Considerations . 51 2.2.5. Technique of Volumetric Analysis . 52 Gravimetric Analysis . 53 Biomedical Analytical Chemistry . 53 2.4.1. Colorimetric Assays . 53 2.4.2. Enzymatic Assays . 58 2.4.3. Radioimmuno Assays (RIAS) . 63

( xiv ) 3. ERRORS IN PHARMACEUTICAL ANALYSIS AND STATISTICAL VALIDATION 71 3A. Errors in Pharmaceutical Analysis . 71 3A.1. Introduction . 71 3A.2. Classification of Errors . 72 3A.2.1. Determinate (Systematic) Errors . 72 3A.2.2. Indeterminate (Random) Errors . 73 3A.2.3. Accuracy . 74 3A.2.4. Precision . 74 3A.2.5. Minimising Systematic Errors . 75 3B. Statistical Validation . 77 3B.1. Introduction. 77 3B.2. Statistical Validation . 77 3B.2.1. Statistical Treatment of Finite Samples . 77 3B.2.2. Distribution of Random Numbers . 79 3B.2.3. Significant Figures . 80 3B.2.4. Comparision of Results . 81 3B.2.5. Method of Least Squares . 83 3B.2.6. Recommendations for Criteria of Rejecting an Observation . 85 3B.2.7. Sampling Statistics . 87 PART II : CHEMICAL METHODS A. Titrimetric Methods: Acidimetry and Alkalimetry 4. AQUEOUS TITRATIONS 4.1. 4.2. 4.3. 4.4. Introduction . 95 4.1.1. Lowry and Bronsted’s Theory of Acids and Bases . 95 4.1.2. Lewis’s Theory . 97 4.1.3. Usanovich Theory . 97 4.1.4. Lux-Flood Concept . 98 Theory of Acidimetry . 98 4.2.1. Direction Titration Method . 98 4.2.2. Residual Titration Method. 98 Assay of Drugs . 98 4.3.1. Direction Titration Method . 99 4.3.2. Residual Titration Method. 100 Theory of Alkalimetry . 101 4.4.1. Direction Tirration Method (DTM) . 102 4.4.2. Residual Titration Methods (RTM) . 103 5. NON-AQUEOUS TITRATIONS 5.1. 5.2. 95 106 Introduction . 106 Theory . 107 5.2.1. Solvents . 107

( xv ) 5.3. 5.4. Methodology . 108 5.3.1. Preparation of 0.1 N Perchloric Acid. 108 5.3.2. Standardization of 0.1 N Perchloric Acid. 109 5.3.3. Choice of Indicators . 110 5.3.4. Effect of Temperature on Assays . 110 Assay by Non-Aqueous Titrations . 110 5.4.1. Acidimetry in Non-Aqueous Titrations . 111 5.4.2. Alkalimetry in Non-Aqueous Titrations .

Preface to the Second Edition Modern Pharmaceutical Drug Analysis essentially involves as a necessary integral component even greater horizons than the actual prevalent critical analysis of not only the active pharmaceutical substances but also the secondary pharmaceutical product(s) i.e., the dosage forms having either single or multi-component formulated product.